CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2016		$ 412,726	$ 11,407	$ 126,462	$ (16,717)	$ (2,846)	$ 531,032
Net income				43,220			43,220
Other comprehensive loss, net of taxes						(1,173)	(1,173)
Cash dividends declared on common stock per share				(9,657)			(9,657)
Issuance costs of common stock		(180)					(180)
Exercise of stock options shares			417				417
Stock-based compensation expense			1,778				1,778
Balance at Dec. 31, 2017		412,546	13,602	160,025	(16,717)	(4,019)	565,437
Reclassification of stranded tax effects (ASU 2018-02) (see Note 17)				709		(709)
Cumulative effect of adopting ASU 2016-01 (see Note 17)				(55)		55
Net income				60,352			60,352
Other comprehensive loss, net of taxes						(4,116)	(4,116)
Cash dividends declared on common stock per share				(9,686)			(9,686)
Exercise of stock options shares			$ 875				$ 875
Net shares issued in satisfaction of performance units earned shares			(819)				(819)
Stock-based compensation expense			$ 1,884				$ 1,884
Balance at Dec. 31, 2018		412,546	15,542	211,345	(16,717)	(8,789)	613,927
Net income				73,395			73,395
Other comprehensive loss, net of taxes						7,642	7,642
Cash dividends declared on common stock per share				(12,958)			(12,958)
Repurchase of stock shares					(12,643)		(12,643)
Exercise of stock options shares			360				360
Net shares issued in satisfaction of performance units earned shares			196				196
Stock issued shares in acquisition of GHB		56,025					56,025
Stock-based compensation expense			2,746				2,746
Balance at Dec. 31, 2019		$ 468,571	$ 21,344	$ 271,782	$ (29,360)	$ (1,147)	$ 731,190